The cause of the Hunley’s sinking has been a mystery since it sank the USS Housatonic on February 17, 1864, and then the Hunley itself mysteriously sank shortly thereafter. This submarine, which had a hand-cranked propeller and a torpedo set at the end of a 16-foot pole, was a desperate attempt by the Confederacy to destroy the Union blockade on Southern harbors that was strangling the economy.

A press release by the Friends of the Hunley, the organization that raised and is conserving the Civil War sub, says that archaeologists have discovered part of the torpedo still attached to the end of the pole. The jagged metal shows that the torpedo exploded its charge of 135 pounds of gunpowder as planned.

Historians used to think the plan was to ram the torpedo into the ship’s side, and then pull away, detaching the torpedo from the pole and then pulling a rope trigger that would explode the torpedo from a safe distance.

Now we can see this didn’t happen. The question remains whether the release mechanism was faulty or if the plan was much cruder – simply ramming the torpedo into the side of the ship and hoping for the best.

It remains unclear if this explosion is what actually sank the Hunley. The submarine’s hull is encased in hardened rock, sand, and silt that the archaeologists are still removing. Only when their job is done will they get a clear idea of how the brave crew of the Hunley met their end.